The present invention in directed to a portable folding chair, such as a beach chair. Specifically, the present invention is an improvement on the portable folding chair disclosed in U.S. Pat. No. 4,482,184--Mincey, which patent is incorporated by reference herein.
The portable folding chair disclosed in U.S. Pat. No. 4,482,184 provides a parallelogram structure that folds in on itself, allowing the chair to be folded up when not in use, and provides telescoping, tubular side structures that allow the chair to be folded up, but which act as support structures when the chair is expanded and used. However, there are a number of problems and deficiencies associated with that chair. One major problem has been that when one is seated on the chair, the chair tends to collapse in on itself if the person leans too-far forward. That is, the shifted weight of the seated person forces the chair into its folded-up position, which the user himself must overcome by providing counteracting moments, which is very uncomfortable. Moreover, if there are not provided the necessary counteracting moments, the chair will collapse, thus potentially injuring, or at least embarrassing, the person.
An additional problem with the chair disclosed in U.S. Pat. No. 4,482,184 is that only after a relatively short period of use, sand and dirt enter into the interior tubing of the telescoping side structures, and into the ball-bearing support of the swivel-mount that allows the chair to swivel. The sand and dirt clog up the interior of the outer tubular elements, preventing the inner telescoping tubular elements from sliding within the outer tubular elements, and prevent, or at least hinder, the upper swivel plate's rotation on the ball bearings. Without the necessary sliding movement between the outer and inner tubular elements of the telescoping side structures, the chair cannot be folded if in an erected state, and cannot be erected if in a folded state, since the relative sliding movement of the inner and outer tubular elements of the telescoping tubular side structures is essential to the proper erection and folding of the chair, and without easy rotational movement of the upper swivel plate, the chair is difficult to swivel.
An additional problem with the chair disclosed in U.S. Pat. No. 4,482,184 is that the chair does not completely collapse or fold. That is, the arm supports of the chair, which are vertically oriented when the chair is in its erected state, do not lie horizontally flush with the base of the chair when the chair is folded. Thus, the folded chair is more bulky and more difficult to carry and transport.
Still another problem with the chair disclosed in U.S. Pat. No. 4,482,184 is that the rear pivot pin of that chair tends to bend over time because of undue stress at its ends.